1. Field of the Invention
This invention relates to a system for communicating to or from one or more UPS devices through a network and, more particularly to a distributed processing system wherein each UPS is connected directly through a network interface unit to a local area network (LAN).
2. Description of the Prior Art
The uninterrupted power supply (UPS) has become indispensable for many modern day power loads. Particularly with respect to computers and other forms of data processing devices, it is of utmost importance that power be uninterrupted so that automated systems do not go down, data is not lost, etc. UPS devices are thus in widespread use for a variety of loads, but are particularly critical to the computer or processor environment.
Of particular importance to this invention is the situation where power on the utility line is lost for sufficient duration that the load must shut down. As is known, in the event of power loss the UPS provides uninterrupted power that looks like utility power, so that the load is unaffected. However, for a given load, any UPS or package of UPSs will be able to maintain power to the load for only a limited amount of time, dependent upon the energy stored in its batteries. In the computer situation, when and if power has been lost for a period of time approaching the total battery time which the UPS can supply, steps must be taken to shut down the load in an optimized manner. For instance, an idle printer or an idle tape drive or terminal could be powered down to conserve the battery for the main frame. Intelligence is thus needed to continuously monitor the time of power loss, and perform sequential preprogrammed load shedding of the computer hardware on the network, in order to maintain necessary operations for as long as possible during a power outage, and to download data onto a storage medium which is not affected by power loss.
The prior art has recognized the need to communicate between a network to which a number of computer loads are attached, and each UPS that is being used in connection with such computers. However, the direction of the solution has been to provide software at the computer, or workstation, which simply enables it to receive alarm and status notification from the UPS. The prior art provides no system or arrangement for sending control signals from an UPS to any other UPS. Further, the prior art does not provide the UPS with the capability of turning itself off or on, or of providing programmed sequential load shedding.
Referring to FIG. 1, there is shown a simplified diagram of the prior art approach to communications involving a network, a plurality of nodes (some of which may be workstations), and a UPS associated with each node. In this arrangement, each UPS is shown powering the load at a network node, although more complicated arrangements are possible. The network nodes are tied together by an appropriate cable, using "EtherNet." See IEEE 802.3 10 Base 5 (thick wire) and 10 Base 2 (thin wire) standards. The EtherNet transports packets of data between nodes, and each workstation uses "Proxy Agent" software to communicate with its respective UPS. The UPS can provide its workstation with alarm and status notification, over the RS-232 link between them. However, not all nodes are workstations, and there is no capability for sending any control or sequence signals from a UPS to any other UPS or directly to any other computer on the network. Further, if any given UPS provides the power to one or more downstream UPSs, the upstream UPS cannot send shutdown instructions to such a downstream UPS. The system is thus limited, and each UPS is without its own capacity to receive and generate controls for itself or other UPSs.